AIE-Active Fluorescence "Turn-on" Bioprobes Mediated by Intramolecular Hydrogen-Bonding for Sensitive Detection of H2S and Visualization in U87 Cells.

Hydrogen sulfide (H2S) is a newly-recognized gaseous signaling molecule and participates in a range of physiological and pathological processes. In this work, based on a molecular switch coupling an imine group with an adjacent H-bond, we designed "turn-on" aggregation-induced emission (AIE)-active fluorescent probes for H2S detection, designated as TSI series. To evaluate the substituents and electron effects on the molecular switch as well as H2S response, four TSI compounds bearing different substituents (HTSI, DFTSI, DPTSI, and DOTSI) were synthesized and compared in the performance of H2S sensing. Among all the probes, DPTSI achieves the best sensing performance toward H2S (> tenfold fluorescence enhancement). Building on these findings, a rational design strategy involving H-bond protection/deprotection and electron-donating group modifications can be employed for developing other probes based on the TSI platform. In further glioblastoma cell imaging assessments, DPTSI effectively lighted up glioblastoma cells with high contrast due to their elevated H2S levels, suggesting its potential as a practical tool for biological H2S sensing and glioma cell mapping in vivo.